چكيده به لاتين
In this research, a novel and simple one-pot process, including mild oxidation of graphite in mixture of H2SO4/KMnO4 at 60˚C was developed to synthesize highly water-soluble graphene nanosheets (GNs) with low-defects in basal plane. In this process, effects of the oxidant amount and reaction time on oxidation and exfoliation degree of graphite were explored. The product was characterized with various techniques including AFM, SEM, TEM, Raman, FT-IR, XPS, XRD and I-V characterization and zeta-potentiometry. Zinc phthalocyanine tetracarboxylic acid (ZnPc(COOH)4) dye was also synthesized by microwave-asisted free-solvent and fast process. hydrothermal treatment was applied for preparation of ZnS nanoparticles capped with 3-mercaptopropionic acid (MPA), ZnO nanoparticles modified with 4,4'-bipyridine (bipy) and CuO nanosheets.
The prepared nanohybrids in this research were based on the obtained ZnS and ZnO nanoparticles. The novel and simple one-pot process was designed for preparation of the ZnS-based nanohybrids. These nanohybrids were divided into two groups. In first group, the ZnPc(COOH)4 dye and the prepared graphene solution were used. The graphene and CuO nanosheets were applied in second group. The ZnO-based nanohybrids were also synthesized using the prepared graphene solution and the ZnPc(COOH)4 dye by the novel and simple method.
By exploring the optical and photoelectrochemical properties of nanohybrids, the optimum value of each component in two and three components nanohybrids, in where photocurrent response was maximum, was determined. All nanohybrids were characterized using several methods such as FT-IR, XRD, PL, UV-Vis, Raman, SEM and TEM. The photoelectrodes including nanohybrides and their components were prepared via drop-casting of sample onto the ITO-glass. The Photoelectrochemical properties of photoelectrodes were explored with methods including chronoamperometry, cyclic voltammetry and electrochemical impedance spectroscopy, under irritation of visible light. The mechanism of electron transfer, photocurrent generation and the role of each component in nanohybrid were evaluated. The designed processes for preparation of nanohybrids and the selected p-semiconductors including CuO and ZnPc(COOH)4 were very effective on enhancing the optical properties and photocurrent generation of ZnO and ZnS compounds in visible region. The added graphene into nanohybrids was also caused to increasing the visible light absorption and effective separation of photoinduced charges that led to the excellent enhancement of photocurrent.
Graphene oxide (GO) nanosheets was also synthesized via modified-hummers method. Then, GO was functionalized with ligands of 2,2'-dipyridileamine (DPA) and 2-carboxaldehide thiosemicarbazone (2-PTSC), in separate runs. The attachment of ligand was comfimed by FT-IR, XRD, XPS, CHNS, SEM and AFM techniques. GO modified with DPA was applied for simoltanious adsorption of Pb2+, Cd2+, Cu2+ and Ni2+ from multiple solution. GO-modified with 2-PTSC was also considered as adsorbent for removal Hg2+ ion from water. The effective variables on capacity of adsorbent including adsorbent dosage, pH, time and initial ion concentration were optimized with using central composite design (CCD). The effect of each variable and interactions among them, on the adsorbtion capacity of adsorbent were studied by response surface methodology. The adsorption mechanism was evaluated by fitting the experimental data into the Langmuire and Frendlich isotherm models. Additionally, the efficiency of adsorbents was examined on some real samples. The selected ligands, the process of modifying graphene oxide, the optimization of variables and using ultrasound power were very effective to enhance the adsorption capacity of graphene oxide.
Keywords: Nanohybrids, graphene, zinc sulfide, zinc oxide, dye, zinc phthalocyanine, cupper oxide, photocurrent, graphene oxide, 2, 2'-dipyridileamine, 2-carboxaldehide thiosemicarbazone, adsorption, optimization.
